Here we model the impact of legacy chemicals on ESA-listed Chinook salmon (O. tsha- wytscha) that spawn in the upper reaches of the Willamette River Basin (henceforth referred to as Upper Willamette River; UWR) in Oregon, USA. Juveniles migrate seaward through histor- ically contaminated Portland Harbor, a designated Superfund site since 2000 (described in detail below).

As a result, those salmon, all less than a year old, are likely not surviving long enough to make it back to the ocean.

But the study also pointed out that there is one thing we can do to help the fish survive.

The researchers said if the contaminants are cleaned up, the salmon population in the Willamette River would increase significantly.

"Our modeling suggests that we may be seeing, in the future, as much as a 20 percent increase in the number of adults that come back to spawn as a function of removing a lot of these toxics in the lower part of the river," said eco-toxicologist Nat Scholz who was also lead author on the study.

The study suggests that as the Portland Harbor Superfund site is cleaned-up, salmon recovery efforts in the Willamette will get a major boost.

The scientists will be back out on the Willamette this summer to do more testing on the fish.